1. Field of the Invention
This invention relates to an anti-skid device for motor vehicles, especially for trucks and heavier vehicles operating under severe conditions, particularly on ice and in snow or the like.
According to a very old idea a device has been proposed, which comprises a rotary spreader carrying a plurality of chain links or the like. The spreader is caused to abut one of the drive tires, and upon rotation of the spreader a number of chains or the like are driven between the tires and the underlying surface to increase the friction therebetween.
Devices according to the aforesaid idea are previously known, for example through British Pat. No. 110,674, French Pat. No. 2 036 889, German Laid Out Document No. 1 162 216, and many more. Although a great number of devices of this kind have been disclosed in patent literature, and several such devices have been demonstrated, not a single one knowingly is used generally in practice today, in spite of the satisfactory operation many of these devices have been alleged having shown when they were demonstrated.
There are several reasons for this phenomenon. Some of the constructions have been relatively complicated and, therefore, expensive. In view of the improvements made with respect to road maintenance and the like, the need of such devices has been deemed not to be sufficiently great to justify the high expenditures. Some of the known devices possibly have operated well under favorable conditions, but in practice may have experienced situations implying really troublesome conditions. One usual reason of failure appears to be the encroachment upon the ground clearance of the vehicle by the device, which thereby was deformed when it contacted stumps and similar terrain obstacles and, subsequently, did not function.
Several different reasons in combination may have prevented the development of a popular embodiment.
The development of the present invention was started with a study of the known ideas and a systematic testing of the disadvantages, in view of the fact that no construction of this kind had achieved wide application so far.
At a long series of experiments an essential problem was found being caused by the immense energy imparted to the outer ends of the chain links. When being guided in a wrong way and striking against suspension or bearing means, the resulting damage is substantial.